脊髓性肌肉萎缩症（英语：Spinal muscular atrophy，简写为SMA），是一种遗传性神经疾病。它会造成运动神经元退化、肌肉萎缩，肌肉无力，最终造成死亡。

控制肌肉的运动神经里的某种蛋白质（运动神经元存活因子，SMN）出了问题，使得神经信号的传递受到阻碍，造成肌肉的收缩失常。控制这种蛋白质形成的基因，称为SMN1，当这种基因出现问题时，就会产生这种疾病。

Proximal spinal muscular atrophy (SMA) is an autosomal recessive disease caused by a genetic defect in the SMN1 gene, which encodes SMN, a protein widely expressed in all eukaryotic cells. SMN is apparently selectively necessary for survival of motor neurons, as diminished abundance of the protein results in loss of function of neuronal cells in the anterior horn of the spinal cord and subsequent system-wide muscle wasting (atrophy).